Pulse-time discriminator



July 29, 1952 A. w. FRIEND PULSE-TIME DISCRIMINATOR Filed Aug. 27, 1946 SIG/VAL l 4 06M EUR my #0 PM m l mm 3 M l m 4 ,2 WW M fa, l 3 M6 I M DA E EN N m m w R 54 us mm m M w m m u my a SUI/1V0 REPRUDl/CER PULSE TIME DISCR/Ml/VAFUR INVENTOR ALBERT W. FRIEND ATTORNEY PULSE TIME M00l/M7/0N FREQSEZECTOR i atented July 29, 1952 *PULs E-rrME nlsonmiNArort Cambridgdjlltlass, -ass ignor to t p 9 Ame c c rnered? Application-August 27, 19.46,.seria1no. 593,321

' .acl i s. (Cl-2 50527 l Thisfinvention relatesrto discriminator. circuits and more particularly to. a time discriminator-for signal. pulses. I In the use of electronicdevices itfoftenibeco'mes necessaryto resolvealtrain ofsignal pulses transmiss-ion of optical images. "Television: systems of the-general character of that disclosed. in

. the patent" to .:Arthur' :.W. Vance, 1N0. 2,137,039,

.4 dated November :15; .1938,..and. assigned. to the.

Radio Corporation ofAmerica, include a cathode scanningofthe transmitting system and the receivinggsystem, an oscillator, is utilized to generate .sharpvoltage peaks', and its oscillation frequency is locked in step with operating action; at

the transmitting station by transmitted synchro- .;nizing impulses whichareapplier tothe oscillating circuit atthe receiver. The tips o f the volt- .age peak referred. to ,which occur at the ends. of .each of the scanning periods are-utilized to drive the horizontal deflection system.

Deviationirom synchronization-will cause dis- I tortionpfthe reproduced image.

According .to this invention an. improved methd and.means are provided tocontr'olithe timing 4.01? the images'canning bythe cathoderaybeam. Intelligence is transmitted throughspace' by; modulation of a signal carrier, for example, a

radio-frequency signal wave, transmission of "the carrier, and demodulation of the carrier at-the receiving station. Modulation'is'the process of alteringaradio frequency signal wave in accord- ;45 h I A I V The pulsestim modulation ire ance with the intelligence to betransmitted.

" Acontinuous radio frequency wavepossesses "three" definite characteristics'amplitude, frequencyand phase. A signaliis saidtobe. frez quency modulateclwhenthe amplitude of thesig- LL nal :carrierrremains. constant :and the frequency of the carrier. is. modulatedv in accordance with the transmitted intelligence.

.. Instead-ofmodulating a frequency of;t he carpmicrowave.v tubes such as the; ma are'n a wfre uen 5399 13 ;-.-ampl tudeemqdul t en. 9

with n. tdlera le. l m tspulses.

h rarv .celfta n .u t a @15 1 .n ell idf ever -Y percenta e i E,

vantages in relay and multi-cha modulate byuiseriminatmg the r time modulated pulses In cdmm mom 'unicatioms t ms push erim nat o .aIrir directly as isadonezin.the conllentionalxi f. .5. ach f e.- -f

3 cut manner by a division of time along a basic time interval.

For purposes of explanation, let there be selected a basic time interval of 100 microseconds. Short pulses may be transmitted to a receiving system completely at any part of this time interval, forexample, a complete pulse may be exchanged in the first tenth of the interval, that is, the first l microseconds. The 100 microsecond interval accordingly may be divided into a number of shorter intervals, say of 10 microseconds each.

It will be seen that if the pulse occurs completely in one 10 microsecond interval of the basic time interval of 100 microseconds, the receiving system would be idle during the other 90 microseconds. However, other pulsesmight easily be delivered during any of the other 10 microsecond intervals. It is obvious that each of several receiving systems may be made responsive to a particular one of these 10 microsecond intervals but not to the other. "In this way a channeling system based upon time division willbe obtained. In practical pulse-time modulation systems, one channel is reserved for synchronizing pulses, thus in a 100 microsecond basic time interval, the first 10 microsecond sub-interval'might be the synchronizing pulse. A receiving circuit would be arranged to receive pulses in any of the channels by making it responsive only during the selected sub-interval as well as to the special synchronizingpulses arriving in the first sub-interval. Such action-may be secured by means of vacuum tube gating circuits of the biased multivibrator'type which keep the receiver inoperative except during the desired reception sub-intervals.

According to this invention, a new and improved method and means are provided for selecting the desired sub-interval in a pulse-time modulation system.

The primary object of this invention is to provide an improved pulse-time discriminator.

, Another object of this invention is to provide an improved synchronization circuit.

, 7 Still another object of this invention is to provide an 'improved synchronizing circuit for a television system.

, ,A further object of this invention is to provide an improved signal'communication system.

A still further object of this invention is to provide an'improved circuit for the discrimination of pulse-time modulation.

Other and incidental objects of the invention 7' will be apparent to those skilled in the art from a reading of the following specification and an inspection of the accompanying drawing in ,volving this invention in another of its preferred forms.

Referring now in detail to Figure 1, there is Zshown an input circuit including condenser l which is adapted to receive a train-of signal pulses, for example, a train of synchronizing pulses employed'in the synchronization of scanning operations. The signal pulses are applied 'tocontrol electrodes 3: and 5 of electron discharge,

devices I and 9 respectively. It will be notedtha't control electrodes 3 and 5' are connected together, so that the input signals are applied to the tubes 7 and 9 in phase.

Discharge devices I and 9 contain anodes II and [3, which are connected in push-pull through transformer 15.

Electron discharging devices I and 9 each contain another control electrode H and I9. Control electrodes I! and I9 are adapted to receive a gate signal voltage, which, with suitable tube bias voltage, will permit tubes l and 9 to be op,-

erative only during time periods when the gate signal voltage is applied on electrodes I1 and IS.

A gate signal voltage may be derived from a deflection signal generator of the type employed in television systems, such as, for example, the deflection circuit shown, and described in the Reissue Patent No. 20,338'issuecl to W. A. Tolson and dated April 20, 1937. The gate signal referred to may also be derived from a biased multivibrator circuit. It is essential for the proper functioning of this invention that the timing of the gate signal coincide with the timing of the inputsignal pulse, whether the timing of the gate signal be derived froma deflection circuit of a television system or from an auxiliary multivibrator circuit.

It is important that the applications of the gate signal to eachof the electron discharge devices and 9 recur at the same frequency and. be overlapping in time interval, but not simultaneous. This causes the discharge devices I and 9 to be operative only during overlapping, but not simultaneous, time intervals recurring at the frequency of the input signal pulse.

By passing the original gate signal through a time delay circuit 26 and applying the gate signal to electrode l9 before delay andto electrode ll after delay, electron discharge devices I and 9 may be made operative only during periodic,

V overlapping, but not simultaneous, time intervals.

It will be seen that, because of the push-push connections of discharge devices I and 9, no signal would pass through the circuit including the discharge devices I and 9 and transformer l5, if both the discharge devices I and 9 were continuously operative. This is because the signal output of each of the discharge devices I and 9 is in phase opposition.

Because the application of the gate signal makes the discharge devices 1 and 9 operative shown in curve B. Curve C representsthe compulse, as indicated by 2|.

bination of the original gate signal shown in curve-A with the delayed gate signal shown in curve B. 7 7

If the incoming signal pulse occurs during time interval t1, only tube 9 will be operative and a pulse signal will be produced in the output circuit of transformer I 5. The output signal in the transformer l5 will take the form of a negative If, however, the incoming signal pulse occurs during time interval 732, at which time both discharge devices 1 and 9 are operative, no signal pulse will occur in the output circuit of transformer 15, because of the rondischarge -device 1 is operative, a positive signal -pulse'2-3 will occur in the output circuit of gate signal-timing is such that the incoming sigi nalpulseoccurs durin'g time intervalta- -however, it the timing of -the gate signal is idelayedsuch push -pushaction of the-:circuit in balancing out he'- amplified-signal pulses. r

1f, :however,the/incoming signal'pulse -occurs uringtim'e interval= ta, at which time only electransformer 15. 1 Itfollows that no signal will be produced'in the output circuit of transformer l as 'long as the -that the incoming signal pulse. occursduring time interval t1, a voltaga occurs in"- the "output circuit of transformerhaving a negative pobe used for changing 'the 'timing of the gate signal v; enerator to bring itupdn step; Likewise, if the ate signal' advances 'in time such thatfithe incomingsignal pulse occurs duringtimeintervalarity.2 As is known in the art,- such a pulse can t3; a signal voltage; of the opp'osi'te' polarity is :produced -in the 'outputcircuit of transformer l 5 andmay be used to delay. the timing of the-gate :volving theuse oftthis invention in-one of its 5' preferred. forms. acts to. maintain synchronism.

K nary of, transformer. I 5.: and provides an? amplified .-.=.':energy. pulse. ..As illustrated, theoutput is taken the ,platercircuit of. tube.25, but it could be .9 takenfrom the cathode circuit.

signal generator. If follows that a system' in- :it Amplifying tube is connected to the second- J The circuit shown in.Figure 1 correspondsto curve -A-. another-form of gate signalwhich may be used in, the practice of anotherpreferred -s-.the.-.pulse' time discriminator shown in block ini-Figure 4 and Figure 5. The gate .signalillus- .trated in. Figure 1 will be developed in the hori ,w zontal; deflection circuit. following .and shown w in block in Figure 4. The gate. signal may also be'developed in a timing multivibrator, as shown in Figure 5.

'- ii'Iurning now to: Figure 3, thereis shown b352 form of this invention. By .passingthegate signalrepresented by. curve A through a delay circuit, curve B results. If the curve B repre.- 4 sentative of the delayed gate signal is subtracted ,from the curve A representative of the undelayed gate signal, curve C will result. A

By properly adjusting the shape of the gate signal, a curve having the straight portion during time-interval i2 is obtained.

put of electron discharge device 9 will be greater than that of electron discharge device I. This will result in a negative pulse in the output circuit of transformer 15. If the incoming signal pulse occurs at the middle of time interval t2, both discharge devices I and 9 will be equally operative and the signal produced by each of the discharge devices will cancel each other out so that no signal pulse will occur in the output circuit of transformer I5. If, however, the signal pulse occurs at the end of time interval t2, electron discharge device 1 will be more operative than electron discharge device 9, and therefore a positive pulse will occur in the output circuit of transformer I5. I

Turning now to Figure 4, there is shown in block diagram 2. television system employing 75 this 'invention intone Itelevision selector 29 obtains signal v'energyiafmm synchronizing :pulses. to pulse-time. discriminator 3.39,;'which ..may ..take 1116 form shown in :the

-- ..-.example, take the form of the; deflection circuit 1.; shown; ands-described in? the. RBiSSIIGTPEtBnt' vNo.

' 20,338issued to. W. A; Tolsonand datedrseptemher. 30, 1937:..-

. under Figured, above: the 1 synchronizing ;signal nator 51. i initial. pulse'from a frequency selector 41. .The synchronizing pulse may. be, 'for. example, the

of. itsspreferred formsa A antenna 3| and passes the imageisignal through theivideo -amplifier 33 to the control: electrode 35 of the image tube 31. Televisiomselector 29 Lmay; for example, be of: the type shown and described in' the reissuepatentto W. L-s carlson, No. 20',' 700;'dated A"pril 19,1938.

1':The television' selector 29-ialso furnishes-signal energy comprising the horizontaltscanning i line circuit diagram 1'. contained in: Figure 1. The ..pulstinie;adiscriminator 39 is connected toithe horizontal rdeflection circuit 4 I which. may; for

1 In accordance" with the detailed description pulse applied to the input circuit of 1311811211188- time .discriminator39 will cause apulse signal in ;the;. output, of pulse-time .discriminatordll the; signal pulses with respect to a gatersignal whose polarity is dependent upon theqtiming of which, in accordance with the form; of the in- .vention shown inv Figure 4,-maybe derived from thepulse-time discriminator 39; .However, if

the timing of the horizontal defiection'circuit should change such that itis ahead ofthe-synchronizingsignal pulse timing, anegative pulse will be fed the horizontal defiection circuit 4|. This-negative-pulse can be employed to delay the timing ofthe horizontal deflection circuit -4I. .Likewise, if, the timing of the horizontal deflection circuit 4 l lagsthe synchronizing pulse input signal, apositive pulse will be furnished thehorizontal deflection circuit 4| and such a -;positive pulse. may. be employed to speed up the timingzoftthe; horizontal deflection circuit .4l.

,It follows; that horizontal deflection circuit 4 1 will remain instep with the-synchronizing pulse input==signals.

commumcation system".employ1ng--pulse-t1me pmodulation.

Turning-now. ton-Figure 5, there 'is'show na l .A frequency selector ll'forv pulse-time modu- ".latedsignals is connected to antenna 49-and itransmits, signal energy to pulse-time discrimi- -A' timing multivibrator 53 derivesits first pulse in a series of pulses as referred to above. The timing multivibrator 53 is adjusted to produce an output signal taking the shape of that shown by curve A in Figure 3. The pulsetime discriminator 5| includes the time delay circuit necessary to provide a similar pulse delayed in time in order to provide an overlapping, but not simultaneous, pulse B. The resultant series of pulses furnished to sound reproducer 55 will be time discriminated inaccordance with the time of arrival such as to produce intelligence in sound reproducer 55.

The timing multivibrator 53 may, of course, be adjusted such that the pulse-time discriminator 5! will operate only during any predetermined time interval. Only thattime interval selected will actuate the sound reproducer 55 because of the balancing effect of pulse-time discriminator tubes explained in. detail above under Figure 1.

Having thus described myinvention, what is .claimedis: g a 1 1. A television deflection system comprising, in

combination, a source of synchronizing pulses, a deflection signal generator having an output circuit,. a pair of electron discharge devices connected in push-push and, each having a pair of .control electrodes, T8,, connection betweensaid source of synchronizing pulses and one ofv said 'icontrol electrodes of each of said electron discharge devices, a connection of substantially no timedelaygbetween said deflection signal genaerator output circuit and another control electrode' of oneof said-electron discharge devices, a

time delay circuit, anda connection through said tim 'delay circuit between said deflection signal -.-generator :output circuit and another control electrode of the other of said electron discharge devices. 1 7

2. A synchronizing circuit comprising in combinatio'n, a source of synchronizing pulses and a source of pulses to be controlled, means for controlling the frequency of said source of pulses to be controlled comprising a-first and second electron discharge-device each having a first and second control electrode, the output circuits of said electron discharge devices being connected in'push-pull, a connection between said source of synchronizing pulses and said first control electrode of both of said-discharge devices, a connection betweensaid source of pulses to be controlled and the second control electrode of said first discharge device, a time delay circuit, the time delay of said time delay circuit being less than the time duration-f one of said pulses, a connection between said source of pulses to be controlled and the'second control electrode of said second discharge device through said time delay circuit, and a coupling between said pushpull output circuits and said frequency control means.

synchronizing signals and said first control electrode of both of said discharge devices, a connection between said source of signals to be controlled and the second control electrode of said first discharge device, a time delay circuit, a connectlon between said source of signals to be controlled and the second control electrode of said second discharge device through said time delay circuit, and a coupling between'saidpush-pull output circuits and said frequency control means.

4. A synchronizing signal input terminal, a synchronizing control voltage output terminal. a frequency controlled signal terminal, a first and second electron discharge device each having a first and second control electrode, the output circuits of. said electron discharge devices being connected in push-pull, a connection between said synchronizing signal input terminal and said first control electrode of both of said discharge devices, a connection between said frequency controlled signal terminal and the second control electrode of said first discharge device,- a time ,delay circuit, a connection between said frequency controlled signal terminal and the second control electrode of said second discharge device through said time delay circuit, and a connection between, said push-pulloutput circuits and said synchronizing control voltage output terminal. I

5. A first periodically recurring signal input terminal, a second periodically recurring signal input terminal, a synchronizing control voltage output terminal, a first-and second electron discharge device each having a first and .second control electrode and an output circuit, the output circuits of said electron discharge devices being connected in push-pull, a connection be- REFERENCES CITED The following references are of recordin the file of this patent:

UNITED STATES PATENTS Number Name Date 1- 2,104,801 Hansell Jan. 11, 1938 2,403,975 Graham July'16, 1946 2,405,238 Seeley Aug. 6, 1946 2,426,225 Krause Aug. 26, 1947 2,427,523 Dolberg Sept. 16,1947 2,433,667 Hollingsworth Dec. 30, 1947 Levey Feb. 22, 1949 

